Electrical transmission of pictures



I- A E N O S T m V F B Oct. 12 1926.

ELECTRICAL TRANSMISS ION OF PICTURES 4 Sheets-Sheet 1 Filed Dec.

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Walker ATTORNEY E. F. WATSON ET AL ELECTRICAL TRANSMISSION OF PICTURESFiled Dec. 20, 1923 4 Sheets-Sheet 2 IN VIEN I'ORS ATTORNEY Oct.12,1926. [1,602,469

E. F. WATSON ET AL ELECTRICAL TRANSMISSION OF PICTURES 4 sheets-sheet 5Fil ed D80. 20 1925 W V 5/ INVENTORS Weaker 4, My

ATTORNEY Oct. 12 1926. 1,602,469

E. F. WATSON ET AL ELHQTRICAL TRANSMISSION OF PICTURES Filed Dec. 20.1923 4 Sheets-Sheet 4 v am 100 /0/ i/ A IN. 'ENTORS E5; Wake/2,11% I/ZWham!" f (A1 a, ,MMMQ

A TTORNE Y Patented Oct. 12, 1926.

UNITED STATES PATENT OFFICE.

EDWARD F. WATSON, OF LARCHMONT, AND ALLAN WEAVER, OF BROOKLYN, NEW

' YORK, ASSIGNORS T AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A. COR-PORATION OF NEW YORK.

ELECTRICAL TRANSMISSION 01 PICTURES.

Application filed December 20, 1923. Serial No. 681,853.

The principal object of our invention is to provide a new and improvedmethod and suitable apparatus for electrically transmitting pictures toa distance. Another object of our invention is to provide for analyzinga picture into small elemental portions and comeapparent onconsideration of a limited number of specific embodiments thereof whichwe have chosen for illustration in the accompanying drawings and to bedescribed in the following specification. will be understood that theinvention is defined in the appended claims and that the followingdescription relates to the particular examples of its practice which arehere set forth for illustration.

Referring to the drawings, Figure 1 is a diagram of apparatus forautomatically preparing a punched tape to represent the picture. Figs. 2to 6 are views of punched tapes obtained under various circumstancesthat will be stated. Fig. 7 corresponds to 1 with the addition ofcounting mechanism to count and record on the tape a sequence of pictureelements of the same shade. Fig. 8 corresponds to Fig." 7 with the addition of apparatus to suspend punching the tape with individual symbolsfor individual picture elements when a certan number of those elementsare all alike and to punch a special symbol for the entire group. Fig. 9corresponds to Fig. 8 except that it shows counting and punch suspendingapparatus for two shades instead of merely one. Figs. 10 and 11 'are,respectively, elevation and top plan views of a detail modification.Fig. 12 is a diagram of receiving apparatus to reproduce the picturefrom a tape corresponding to the transmitting apparatus of Fig. 9.

Referring to Fig. 1, the rotating drum 22 has a' relief film 21 wrappedround it, the degree of relief correspondingwith the lights and shadesof the picture to be transmitted. The drum 22 is rotatedand at the sametime traversed relatively slowly in the direction of its axis, so thatthe stylus 27 in engagement with the film 21 traces on the cylindricalfilm 21 a helical path.

The shaft carrying the drum 22 also carries a rotating wiper 23 inengagement with a fixed conductive segment 24 whereby the circuit of thebattery 25 is completed through the wiper 23 and the segment 24 to thecarbon microphone 26 whose resistance is governed by the stylus 27. Thecurrent from the battery 25 will vary in accordance with the relief ofthe film 21 as it is engaged by the stylus 27, and this varying currentthrough the resistance 28 will vary the electromotive force on the gridof the three-electrode vacuum tube amplifier 29.

The output or plate current from the amplifier 29 goes through the threerelays 30, 31 and 32 in series. These are marginal relays. None of thempicks up for a current corresponding to a degree of relief of the film21 corresponding, in turn, to white in the picture. For' light grey, theoutput current from the amplifier-29 will be enough to cause 30 only topick up. For dark grey, the current will be enough to cause relays 30and 31, but not 32, to pick up and for black in the picture the currentfrom the amplifier 29 will be enough to cause all three relays 30, 31and 32'to pick up.

The well known five-unit printing telegraph code is employed except thatcertain combinations represent difi'erent shades of picture elementsinstead of representing letters of the alphabet as in printing teleg--raphy. Y

A length of tape 37 is shown in Fig. 2.

This is fed step-by-step in the direction of its length by astar wheelengaging the perforations 39. The five plungers 41, 44, 34, 47 and '54of Fig. 1 correspond to the five positions indicated by the numerals 1,2, 3, 4 and 5 in Fig. 2. The drum 22 rotates stepby-step carrylng thewiper 23 one step at a time across successive contact segments 36.

At each such step the punch magnet 35 is normally operated, and itpunches in the tape 37 a transverse row of five holes or lesscorresponding to the plungers 41, 44, 34, 47 and 54 that are actuated byenergization of their respective magnets. Operation of the punch magnet35 also operates the star wheel to drive the tape 37 by engagement with"its perforations 3 Assume that a portion of the film 21 of reliefcorresponding to white in the picture is passed step-by-step under thestylus 27; accordingly none of the three marginal relays 30, 31 and 32is actuated. It will readily be seen that of the magnets 40, 43, 33 and46 only 33 has its circuit closed. This willadvance the bar 34, and thepunch magnet 35 will punch a series of holes 38 in the third position as111 Fig. 2.

When the shade is light grey, marginal relay 30 will be actuated toclose the circuit of relay 40 and advance the bar 41 in addition to 34,and the record punched in the tape 37 will be as shown at 42 in Fig. 5.

When the picture shade is dark grey, both marginal relays 30 and 31 willbe actuated, and the bars 41 and 44 will be advanced in addition to 34,and the symbol punched in the tape 37 will be as shown at 45 in Fig. 5.

\Vhen the picture shade is black, all three marginal relays 30, 31 and32 are energized, the circuit for. 33 will be broken at 32, and thecircuit for 46 will be made at 32 so that the record willbe made asshown at 48 in Fig. 5. It is assumed that the bars 41, 44, 34', 47 and54 and the punch magnet 35 are the usual parts in a wellknownfive-element printing telegraph tape-punching machine in which thecode combinations 38, 42, 45 and 48 correspond to certain letters orother characters according to the following table:

Code Current strength Corresponding Modified characi i sgg in marginalre- Relays actuated. ggiggfi g $5 553 regular printer ters for recordplays. Spaces) characters. ing picture.

White. Lowest. None. 34. e -o Space. Space. Light grey. Next to lowest.30. 41 and 34. oo S. Small (lot. I Dark grey. Next to highest. 30 and31. 41, 44 and 34. ooo- U. Medium dot. Black. Highest. -30, 31 and 32.41, 44 and 47. oo-o-- J. Heavy dot.

-- 51. 47. 0 Carriage re- Carriage return. turn." 52. 44. o Line feed."Line feed."

In the foregoing table it will .be seen that in addition to the fourpicture shades, code combinations appear for carriage return and linefeed. It is assumed, as will be described presently, that at thereceiving end the picture is recorded on a page 'print lines of theforegoing table and as shown at 48 and 48 in Figs. 5 and 6/ At thereceiving end a page printing telegraph receiver is employed with areduced line feed to bring the lines close together and with the lettersS, U and J replaced, respectively, by type to make a small dot, a mediumdot. and a large dot. Thus it will be seen that the page in thereceiving printer reproduces the lights and shades of the picture infour degrees of shade, white, light grey, dark grey and black, giving ahalf tone picture. lVhen viewed at a distance or when reducedphotographic-ally, this makes a very good half tone picture.

It will readily be understood that in many pictures there will beconsiderable regions of uniform shade for which with the apparatus ofFig. 1 the symbols punched in the transmitting tape will be repeatedalike for 'considerable length as, for example, for a white shade inFig. 2. Preliminary to dis closing how the length of the tape, andaccordingly the line time, can be economized for these repetitions oflike shade, we will describe in connection with Fig. 7 apparatus forcounting and recording in thetape groups of ten successive white pictureelements. Fig. 7 is substantially like Fig. 1 with the addition that themagnet 53 for the fifth selecting bar 54 is connected to countingapparatus, and the back contact of the first marginal relay 30 isconnected to magnet 56 which controls said counting apparatus now to bedescribed.

Whenever white picture elements are be ing repeated, as in Figs. 2 and3, the magnet 56 will be energized and close battery and ground for thecounting relays 58. Each time the punch magnet 35 operates, the relay 57in series therewith will operate momentarily and cause a counting relayto pick up and lock up. There are nine of these counting relays numberedfrom 1 to 9. and when the ninth hole for the white shade is punched inthe tape, as at 38 in Fig. 3, the relay 9 of assembly 58. will pick upand close thecirouit for relay 59. which in turn will close the circuitfor relay 53 and advance the bar 54 (referring to Fig. 1)

so' that on the next operation of the punch magnet 35, ltherecord on thetape'will appear as at 55 in Fig. 3.

When the relay 9 of assembly 58 was energized, it closed a circuit forrelay 78 which looked up through a front contact. The 10th operation ofrelay 57 causes magnet 9 to release which-closes a circuit for theslow-release .relay 79 which opens the circuitfrom battery to thecounting relays and releases them. The 10th release of 57 shorts outrelays 78 and 79 which allows them to release and the systemis ready toI begin another count. The relay 79 is made slow-release to insure thatit releases later than relay 78.

- If at any time during a count of-a se-" quence of white picture'elementsythe shade changesshort of ten such elements, the -re-" lay 30will thereupon break the circuit of magnet 56 which in turn will releasethe circuits for the counting relays, and they I will go back to theirinitial condition; i

With the preceding explanation of Fig. 7,

it will nowbe convenient to explain, incon-' nection with Fig. 8, howthe tape isshortened by omitting like repeated records for the wh teshade. 1 The apparatus of Fig. 8 is white. Accordingly for a sequenceofwhite picture elements passing under thestylus 27' the armature ofrelay 61 remains on its back contact and keeps the relay 62 energized,closing the circuits for the counting relays 58 which" are like 58 inFig.v 7. WVhen the relays58' have counted up. to 9, relay 9 closes thecircuit forrelay 59; and on the next impulse the fifth hole 55 ispunched along with the third hole 'to indicate ten units of white shade.Thus as a succession o10 white elementspass stylus 27, the first ofthese comes under stylus 27 andthe next punching operation punches thenumber 3to indicate white shade and also the number 5 toindicate'lO'units of this shade.

When the relay 59 is :energized, following the 9th elementofwhiteshadetopass .27, it closes a circuit that begins the count operates andcloses a shunt around the punch -magnet 57. Therefore the punch magnetisarrested until the count of 10 elements past stylus 27 is completed.Then.

the next release of relay 57 operates relay 10 of group 58", releasingthis group. In this way the record shown in Fig. 3, as made by theapparatus of Fig. 7, is reduced to the record shown-in Fig. 4, as madeby the apparatus of Fig. 8.

It will be seen that the shortening of the? tape as in Fig. 4 comparedwith Fig. .3,

will result in a decided saving of line time in transmission. i

The foregoing explanation of Figs. .7 and 8 shows that for apparatusarranged in ac-:

cordance therewith, the economy of tape and of line time is practicedonlyfor the white shade. This is likely to. be one of the commonestvshades in a picture, the next most. common shade being black, and theinter-' mediate shades less common. In Fig. 9 a.

' further modification is shown for. counting and shortening the tapefor repeated picture. elements of either white shade or black shade.Fig. 9 corresponds substantially with Fig. 8 except for certainadditionsthatwill' now be pointed out.

Instead of a single marginal relay 61, as in Fig.. 8, a

plurality of marginal relays 30", 31' and 32 are employed. It will beseen in Fig. 9 that the relays 63, 64, 65 and 66 are-so controlled bythe marginalrelays 30, 31 and 32 that the relay -62 is energized, whennone of the relays; 30, 31 and 32' is ener-' gized and when all of'them'(particularly 32) are energized. Accordingly the relay 62 is operatedboth'for the white shade and the black shade andthe counting re-.

lays 58 and 58 are operated for either shade. Fig. 5 shows how a tapewould be punched with counting, but without shortening, for 10 whiteimpulses, then 10 black impulses, then 10 white, followed by one lightgrey, one dark grey," one black, carriage return, and line 'feed.' lViththe appartus of Fig. 9, this would be shortened as shown in Fig. 6. i a

Figs. 10 and 11 show a modification at the sending end. Instead of theapparatus shown in Figs. 1, 7, 8 and 9 in series with the battery 25 andresistance 28, we may introduce'the terminals of the photoelectric cell'77 in the circuit of that battery and resistance. In this case 7 O isthe regular carriage of a printing. telegraph macl11ne,used to providemeans for moving the film so that it can be tested element by elementand line by line. An auxiliary carriage 71 is mounted above it, and thefilm 72 passes between them. 'A housing, consisting of two parts 73 ,and73 fitting close to the film on opposite sides thereof, is provided. Inthe part 73. is the light source 7.4 and the lens 75 to direct a beam oflight through a narrow spot of the film 72. In the part of the housing73 is another lens 76 which directs the beam of light to thephotoelectric cell 7 7. Accordingly the current in the circuit of thecell 77 is made to vary in correspondence with the light striking thecell which in turn varies in accordance with the degree of transparencyof the part of the film 72 interposed in the path of the light.

In this case the straight conductive bar 2% takes the place of thesegment 24 of Fig. 1 and is engaged by the contact 23 which travels withthe carriage, and at the end of each line of travel of the carriage thecontact 23 engages the contacts 49 and 50' and actuates the carriagereturn relay 51' and the line feed relay 52'.

Suitable receiving apparatus is indicated or shown in Fig. 12. The tapeat the transmitting end abbreviated as described, is used to send codeimpulses over the line, and by means of these a similar tape isreproduced at the receiving end. This received tape is then fed to atape transmitter 102 controlling a page printer which prints thepicture, element by element in succession, according to the code givenearlier in this specification; that is the code for white prints blank,the code for light grey prints a small dot, the code for dark greyprints a medium dot, and the code for black prints a heavy dot. Butwhenever the tape contains a hole in the fifth position this means thatthe shade indicated by the corresponding code shall be printed tentimes. The apparatus by which this is effected is shown in Fig. 12.

When there is no hole in the fifth position in the tape, the operationof the tape transmitter is normal and the feed magnet 103 is energizedfor each revolution of the sending distributor brush which is equivalentto each operation, of therecording printer. However, when there is ahole in the fifth position of the tape, a circuit is completed from theground through contact 100 on the startrelay and through relay A tobattery. This operates relay A which looks up and transfers the normaltape feeding circuit from the feed magnet 103 to relay B. Then, as thefirst character is printed, relay B is energized from battery throughcontact 101. This causes the operation of relay 11 and, as soon as Breleases, operates relay 11". bimilarly, as the second character isprinted. relays 12 and 12' are operated. On the printing of the ninthcharacter, relays 19 and 19 operate in a similar manner and when 19operates. it causes the operation of relay 20 which locks through afront contact. Then, as the tentlbcharacter prints, relay B is againvenergized and relay 19 is released, causing the operation of relay 20which releases all of the counting relays excepting 20 and 20 and alsoreleases relay A. This, in turn, releases relayB which,

through its back contact, releases relays 20 and 20 so that the systemis restored to normal for the 11th character. In the meantime, theoperation of relay 2O has closed the regular tape feeding circuitincluding magnet 103, so that the tape has stepped forward to the nextcode while the tenth character was being printed.

We claim:

1. Means to automatically transmit electrical currents corresponding tothe degrees of light and'shade in a succession of picture elements, andmeans to send a modified current for a succession of elements of likeshade and thereby economize the time of transmission.

2. Means to punch a tape with symbols corresponding to the degrees oflight and shade in a succession of picture elements, and means to punchin said tape a single code symbol for a succession of picture elementsof like shade whereby the length of the tape is shortened for repeatedpicture elements of like shade.

3. Means to automatically transmit electrical currents corresponding tothe degrees of light and shade in a succession of picture elements,means to count a succession of picture elements of like shade, and meansto transmit a current of special character corresponding -to the rcsultof such a count, said special current indicating the degree of shade ofthe counted elements and their number.

4. A picture film varying in character to represent the lights andshades of the picture, a plurality of exploring means for simultaneouslyexploring separate elements of said film, a plurality of marginal relayscontrolled by certain of said exploring means, and means to punch a tapein correspondence with the operation of the marginal relays.

5. In a picture transmitting system employing a punched tape and a pageprinter at the receiving end, means to prepare the tape at the sendingend comprising relays to punch carriage return and line feed symbols inthe tape, and a commutator operated in connection with the transmittingfilm to actuate said relays at the end of each cycle of movement of thetransmitting film.

6. Means to prepare a perforated tape for the transmission of a picture,comprising means to punch a distinctive set of holes in the tapecorresponding to distinguishable shades in the respective pictureelements, means to count a definite number of like shaded pictureelements in succession, and means to punch a distinctive set of hoIes inthe tape upon the completion of such a count.

7. Means to prepare a perforated tape for the transmission of a picturecomprising I means topunch a distinctive'set ofhole's in shades in therespective picture elements, means to count a definite numberof likeshaded picture elements in succession, means to punch a distinctive setof holesin the tape upon the-completion of such a count, and meanstorelease the countin mechanism andrestore it to initial condition whenthe shade changes short of the completed count.

8. Means to prepare a perforated tape for transmitting a picturecomprising primary means to explore a picture film passing successivelyfrom element to element thereof,

auxiliary exploring means a certain number of elements in advance ofsaid primary means, counting means controlled by said auxiliaryexploring means, means to punch a distinctive symbol in the tape whenthe said auxiliary exploring means counts up to the number ofintervening picture elements, and means to arrest the further punchingof the tape while that same number of elements is explored by theprimary exploring means.

9. Means to prepare a perforated tapefor picture transmission comprisingmeans to punch the tape distinctively in correspondence with the degreeo'f'shade of successive picture elements, means to count in advance asequence of picture elements of like shade and upon the completion ofsuch count to punch a distinctive symbol in the tape, and meansthereupon to arrest the further punching of the tape for such sequenceof like picture elements.

10. Means to explore a picture element by element for the degrees ofshade thereof, a plurality of devices adapted to -re-- spondrespectively for the differentdegrees of shade, and means controlled bysaid devices to record code combinations for the respective 'de rees ofshade, said last mentioned means eing adapted to make a single recordindicating the number and shade of the elements in the sequence.

11. A picture film varying in character to represent the lights andshades of the picture, means to explore simultaneously a plurality ofelements of said film, a plurality of marginal devices controlled bysaid means, "and means to make a'code record in correspondence with theoperation of the marginal devices.

12. The method of electrically transmitting a picture which consists inautomatically sending electric currents corresponding to successivepicture elements and send- .ly sending code impulses corresponding tothe degree of light and shade in successive picture elements,automatically counting a definite sequence of picture elements of likeshade and sending a special code combination for such sequence insteadof successive like impulses for the elements thereof.

15. The method of electrically transmitting a picture which consists intesting its elements successively for degree of shade, automaticallycounting a sequence of elements of like shade, making a single record ofthe results of said count, automatically sending code impulsescontrolled by said single record to indicate the shade and also toindicate the count as aforesaid, and reproducing the picture element byelement from the received code impulses.

16. The method of electrically transmitting a picture which consists intesting its elements successively for degree of shade,

automatically counting a sequence. of elements of like shade, making asingle record in code symbols to indicate the shade and also to indicatethe count as'aforesaid, automatically transmitting currents determinedby said code symbols, and reproducing the picture element by elementfrom the received currents.

17. The method of electrically transmitting pictures which consists insimultaneously testing a plurality of separate picture elements, sendingcurrents in accordance with the tone value of one element being tested,recording the tone value of another element being tested, and subsequent1y sending currents in accordance with the recorded test. p

18. The method of electrically transmitting a picture which consists inmaking a plurality of tests of the same picture elements, sendingcurrents in accordance'with the results of one test and simultaneouslyrecording results of the other test and subsequently sending currents inaccordance with said other test.

19. In a picture transmission system, means for exploring successiveelements of a picture to be transmitted, means for antomatically makinga single abbreviated code record of the number of elements in a sequenceof like shade" and of the demeans for testing elements of the picture tobe transmitted, means for'automatically sending code currentscorresponding both to the number of elements in a sequence of like shadeand to the shade of the elements of-said sequence, means to receive saidcura single code combination of the number N rents, and means toreproduce said' picture of counted elements and' their degree of inaccordance with said received currents. shade.

21. In a picture transmission system, In testimony whereof, We havesigned our I means for exploring successive elements of names to thisspecification this 19th day of a picture to be transmitted, means forDecember, 1923.- counting the number of elements in a sequence of likeshade, and means for au- EDWARD F. WATSON. tomatically making a recordin the form of ALLAN WEAVER.

DI so L Al M E R I 1,602,469.Edmrd F. Watson, Larchmont, and AllanW'eaoer, Brooklyn, N. Y. ELnc'rRIoAL TRANSMISSION or PICTURES. Patentdated October 12, 1926.

Dlsclaimerfiled September 12, 1934, by the assignee, American Telephoneand Telegraph Company.

Hereby enters this disclaimer'to the said claims of said Letters Patentwhich are in the following words to wit:

1. Means to automaticallytransmit electrical currents corresponding tothe degrees of light and shade in a succession of picture elements, andmeans to send a modified current for a succession of elements of likeshade and thereby economize the time of transmission.

2. Means to punch a tape with symbols corresponding to the degreesoflight and shade in a succession of picture elements, and means to punchin said tape a single code symbol for a succession of picture elementsof like shade whereby the length of the tape is shortened for repeatedpicture elements of like shade.

3. Means to automatically transmit electrical currents corresponding tothe degrees of light and shade in a successionof picture elements, meansto count'a succession of picture elements of like shade, and means totransmit a current of special character corresponding to the result ofsuch a count, said special current indicating the degree of shade of thecounted elements and their number.

6'. Means to prepare a perforated tape for the transmission of a picturecomprising means to punch a distinctive set of holes in the tapecorresponding to distinguishable shades in the respective pictureelements, means to' count a definite number of like shaded pictureelements in succession, and means to punch a distinctive set ofv holesin the tape upon the completion of such a count.

7. Means to prepare a perforated tape for the transmission of a picturecomprising means to punch a distinctive set of holes in the tapecorresponding to distinguishable shades in the respective pictureelements, means to count a definite number of like shaded pictureelements in succession, means to punch a distinctive set of holes in thetape upon the completion of such a count, and means to release thecounting mechanism and restore it to initial condition when the shadechanges short of the completed count.

10. Means to explore apicture element by element forthe degrees of shadethereof, a plurality of devices ada ted to respond respectively for thedifferent degrees of shade, and means control ed by said devices torecord code combinations for the respective degrees of shade, said lastmentioned means being adapted to make a single record indicating thenumber and shade of the elements in the sequence.

12. Themethod of electrically transmitting a picture which consists inautomatically sending electric currents corresponding to successivepicture elements and sending special modified currents for a sequence ofpicture elements of like shade and thereby economizing the time oftransmission.

13. The method of electrically transmitting a picture which consists inautomatically sending code combinations corresponding to the degree ofshade of successive picture elements, automatically counting a sequenceof picture elements of like shade, and sending a special code on thecompletion of such count, said special code indicating the shade andnumber of the counted elements.

14. The method of electrically transmitting a picture which consists inautomatically sending code impulses corresponding to the degree of lightand shade in successive picture elements, automatically counting adefinite sequence of picture elements of like shade and sending aspecial code combination for such sequence instead of successive likeimpulses for the elements thereof.

19. In a picture transmission system, means for exploring successiveelements of a picture to be transmitted, means for automatically makinga single abbreviated code record of the number of elements in a sequenceof like shade and of the degree of said shade.

21. In a picture transmission system, means for exploring successiveelements of a picture to be transmitted, means for counting the numberof elements in a sequence of like shade, and means for automaticallymaking a record in the form of a singe code combination of the number ofcounted elements and their degree of sha e.

[Ofiict'al Gazette October 9, 1984.]

